1. Field of the Invention
This invention relates to a hot water heater and in particular water heaters of the kind which are instantaneous flow heaters utilizing electromagnetic energy confined within a resonant cavity for heating.
2. Description of the Prior Art
Many different types of water heaters or auxiliary source heaters are known that heats water for residential, commercial, industrial and recreational vehicle use. Typically electric and gas water heaters usually are of tremendous size, require some energy consumption to maintain a storage temperature, are relatively inefficient due to the heat transfer techniques they utilize for operation, and suffer from slow recovery rates. Instantaneous heaters, such as electrode flow heaters, have the disadvantage of high maintenance costs resulting from the destruction of their electrodes.
One solution to these problems is to provide high frequency energy as the heating source in a tankless hot water heater system. It is well known that an increase in temperature is observed in materials exposed to electromagnetic radiation within the microwave portion of the spectrum, as demonstrated in high-frequency heating devices or microwave ovens. The rapid and efficient heat transfer means associated with microwave radiation can be applied to a resonant cavity structure which replaces the tank of the conventional storage hot water heater. For example, U.S. Pat. No. 3,891,817 issued to H. Brown on June 24, 1975, illustrates a water heater assembly that combines a heat exchanger, a source of microwave energy, a heating container for water, and a means to circulate water from a storage tank to said heating container which is controlled by a temperature sensor in the storage tank to maintain a predetermined water temperature.
U.S. Pat. No. 3,535,482 issued to J. H. Kluck on October 20, 1970 illustrates an apparatus for the rapid heating of fluid materials that converts electromagnetic energy into thermal energy within a fluid stream. The fluid is heated as it flows through a length of tube that passes transversely through a waveguide. A conducting tubular member is positioned adjacent to the passage of the tubing through the waveguide to prevent the radiation of energy from the waveguide. The pressure required to maintain the proper flow conditions for heating is provided by a pump and valve control system.
The prior art has utilized electromagnetic energy for the rapid heating of fluids and has disclosed various methods to prevent electromagnetic energy from radiating beyond the heating apparatus. However, for the most part, such teachings have not provided electrical isolation of the cavity from the external surface of the heater that is required for an instantaneous, tankless heating system and that accommodates fluids through the cavity without flow impairment. Prior art references have not disclosed an instantaneous heating apparatus that is controlled by conditions of fluid flow through the heating unit during use in a conventional pressurized water supply system. Accordingly, there is a need in the art for a water heating apparatus that utilizes energy for heating only when a demand for hot water exists and operates efficiently with an electromagnetic energy source.